1. Field of the Invention
Embodiments of the present invention generally relate to a method of forming micro-electromechanical system (MEMS) based cantilever switches within an aluminum or copper back end of the line (BEOL) system or any semiconductor process having a metal interconnect system.
2. Description of the Related Art
For MEMS cantilever switches the gradient stress through the beam requires stringent control to prevent significant curvature upon release. Curvature of the beam is when the beam does not return to its normal position prior to contact with an electrode. The beam remains close to the electrode and thus the power necessary to move the beam into contact with the electrode may change.
When the beam develops curvature, the switch may not operate according to its designed parameters. For example, when the beam develops a curvature, the beam remains closer to the contact electrode. Thus, the amount of power necessary to pull the beam into contact with the electrode may be reduced. The switch or beam may therefore be brought into contact with the contact electrode inadvertently. Additionally, because the beam has a curvature, the switch may not operate in a predictable manner. Without knowing the curvature and the power necessary to pull the beam into contact with the contact electrode, control of the switch may be erratic. The curvature in the beam can force the switch to move up or down with respect to the normal position (i.e., the ideal case). Therefore, the voltage required to make the device move from the initial starting position with respect to the normal position can change.
The curvature specification becomes significant as the beam thickness is reduced below 200 nm due to the increasing effect of compressive stress relative to the natural columnar grain structure of the material. The use of refractory materials, such as TiN, to form these very thin cantilever beams exhibit significant gradient stress in the deposited film due to the manner in which the film nucleates and grown upon the wafer surface. In order to tightly control this gradient stress, stringent deposition control parameters are required.
Therefore, there is a need for MEMS cantilever switch that overcomes the gradient stress and a method of its manufacture.